1. Field of the Invention
This invention relates to a method and an apparatus for sorting fruits such as apples, peaches, pears, persimmons and tangerines and vegetables such as tomatos, melons and water melons according to sorting standards and the standards desired in the market of destination (the areas of consumption).
2. Description of the Prior Art
The grading standards define quality in terms of appearance and do not show it in specific values because the definition is based on judgement by visual examination. Each fruits sorting facility is, therefore, training sorters by showing them grade samples (either the actual fruits or color pictures). However, the results of such grading judgement by sorters varies and are inconsistent due to the persons, sorting time zones, sorting facilities and areas. As a result of such inconsistently, a fruit judged to be "good" sometimes tastes better than a fruit of the same kind judged to be "excellent". This has lowered the reliability of quality grading.
To solve this problem, therefore, research has been conducted during recent years for measuring apparatuses using sensors of various kinds. However, with the exception of some special types that are applicable only to a specific subject among many subjects of inspection and some test apparatuses, these apparatuses have not been put into practice as yet.
These sorting apparatuses of the prior art perform sorting by standards for classification by weight or standards for classification by outside dimensions. They are arranged to sort solely by weight or solely by shape according to their specific purposes and are thus arranged in varied manners. The apparatuses of the type arranged to sort by weight permit sorting without ambiguities irrespectively of difference in the operator and the machine, because weight measurement do not involve any factors of inconsistency except the mechanical performance of the apparatus used.
The sorting apparatuses of the type sorting by shape on the other hand have the following problem: The objects to be sorted include objects that have a distinct measuring position or point such as the length of a cucumber or the diameter of a tangerine (the diameter of a sieve opening) and those that have an indistinct measuring position or point such as the outer diameter of a somewhat distorted spherical mass such as apples, peaches, pears, melons, etc. which have longer and shorter diameters. The former type has a distinct measuring point and has no factor of inconsistency except the performance of the machine irrespective of differences in the operator and the machine. In the case of the latter type, however, the indistinct measuring point results in inconsistent and ambiguous results of measurement according as the operator and/or the machine varies.
In view of the above, there have been proposed various universal shape sorting apparatuses for fruits and vegetables of spherical mass shapes. Typical examples of the sorting apparatuses of this kind include shape sorting apparatuses of the mechanical contact type measuring distance between two points (called a gap type) which have been disclosed in Japanese Patent Publication No. Sho 56-38268 and Japanese Utility Model Application Laid-Open No. Sho 51-86448 umbrella shaped spheroidal shape sorting apparatuses of the whole circumference contact type which have been disclosed in Japanese Utility Model Publication No. Sho 39-33455 and Japanese Utility Model Publication No. Sho 56-11978; sorting apparatuses of the light beam type arranged to measure the outer diameter of an object in a non-contact manner which have been disclosed in Japanese Utility Model Publication No. Sho 56-33957 and Japanese Patent Application Laid-Open No. Sho 55-29760; and a shape sorting apparatus of the type arranged to pick up an image by means of a TV camera and to compute the area of the image as disclosed in Japanese Utility Model Publication No. Sho. 56-11980.
The shape sorting apparatus of the contact type measuring the distance between two points is shown in FIG. 1 of the accompanying drawings. In this case, a fruit is laid down in a sidewise posture and its body diameter is measured through a gap distance between two points. The arrangement permits simplification of the apparatus. The fruit can be smoothly discharged as it is to be rolled sidewise in discharging it. The skin of the fruit is not damaged by its stem as it is to be rolled sidewise when discharged. However, the imperfect spherical shape of the fruit which has larger and smaller diameter portions lowers the accuracy of the sorting operation of the apparatus. The inaccurate sorting then necessitates use of human judgement at the time of packing and packaging. The apparatus of this type is therefore inferior in terms of efficiency and labor saving.
The shape sorting apparatus of the whole circumference contact type is shown in FIGS. 2 and 3. Each fruit is vertically put into an umbrella-shaped device. It may appear that the fruit can be accurately sorted by the diameter of the girth of the fruit. However, even a slight vibration causes a difference in the falling point of the fruit. Besides, the structural arrangement of the apparatus is complex. Another shortcoming of this type resides in the relatively long falling distance of the fruit which tends to damage the fruit due to the falling impact.
The light beam type sorting apparatus is arranged to sort by measuring the fruit without touching it. It is thus an advantage of this type that the fruit can be sorted without damaging it. On account of this, the sorting apparatus of this type is becoming most popular. However, in this type, the measuring points are limited to the travelling direction (or the longitudinal direction) of the fruit and the direction of width. This limitation necessitates an arrangement to convey the fruit in an upright posture. Therefore, as shown in FIG. 4, the skin of the fruits tend to be damaged by their stems as they tumble over headlong when discharged. It is another shortcoming of this type that the discharge point is fixed because backets are arranged to be tilted at a predetermined point for every sorting rank. The camera type sorting apparatus also has the same shortcomings.
Each of these shape sorting apparatuses is arranged solely for shape measurement with a measuring device paired with a conveyor which is generally called a bucket conveyor or a sorting conveyor and cannot be arranged in combination with other measuring devices. They show no concept of making them capable of measuring the weight as well as the shape of the objects to be sorted.
Meanwhile, the weight type sorting apparatuses have been improved year after year. These improvements include apparatuses which have been recently developed by utilizing electronic weighing instruments. The structural arrangement of the apparatuses of this type can be divided into two kinds. In one kind, the bucket (a weighing container) which is arranged to carry the fruit thereon is supported by Roberval mechanism forming a parallelogrammic linkage as a weighing mechanism (Japanese Utility Model Application Laid-Open No. Sho 53-148943; Japanese Patent Application Laid-Open Nos. Sho 57-8770 and Sho 57-12864). In the other kind, the fruit is weighed with the bucket of a simple cup shape supported by a balance (Japanese Utility Model Application Laid-Open No. Sho 52-159957). Meanwhile, the discharging methods adopted by these apparatuses include a method of discharging the fruit straight downward as shown in FIG. 5 and a method of discharging the fruit sideward.
In every one of these weight type sorting apparatuses, the weight of the fruit is measured with a sliding piece arranged either below or on one side of the bucket which travels over a weighing device. Therefore, to have the fruit positioned in the middle of the bucket, a deep bowl shaped receiving tray is employed. However, the deep bottom of the receiving tray requires the discharging operation to be done by tilting it to a great degree. Such a discharging operation tends to damage the fruit. Further, since sorting is effected through a classifying discharge device, it is a shortcoming that the discharge points are spaced at fixed intervals in the same manner as in the case of the light beam type shape sorting apparatuses. Further, the bucket and the weighing device are paired with each other for the single specific purpose and the bucket cannot be used in combination with a measuring device of a different type. There is seen no concept of arranging the apparatus to be capable of sorting both by shape and by weight.
In the meantime, intensified competition among producing areas has forced farmers either to change the kinds of their produce or to diversify the kinds. Hence, it is not economical to separately install a shape type sorting apparatus and a weight type sorting apparatus for the diversified kinds of produce. It is therefore desired to have a fruit sorting apparatus capable of sorting both by weight and by shape.
While some markets desire that shipments of fruits be sorted by shape, other markets desire to have shipments of the same fruits sorted by weight. Some areas of consumption prefer a high sugar content in produce while other areas prefer a sourish sweet taste for the same kind of produce. At present, however, there is no sorting apparatus that is capable of meeting such requirement.
Some fruit sorting facilities are installed for producing farmers located in sloping hillside areas while other facilities are installed for farmers located in flat land areas. Assuming that the same kind of produce or fruit is produced by those farmers located in such different kinds of areas, the height of the fruit produced in the hillside area differs from that of the fruit produced in the flat land area as shown in FIG. 6 even if they have the same circumference or girth. In case where sorting is carried out by shape, the farmers who produced the taller fruit in the hillside area are paid less for the amount of produce than the farmers of the flat land area because the same price applies to the same grade. In view of such unfairness, it is desired to use a fruit sorting apparatus which is capable of measuring the height of the fruit for fair pricing.